This disclosure relates to a vaporized fuel processing apparatus including a canister equipped with an adsorbent capable of adsorbing vaporized fuel generated in a fuel tank, and a closing valve provided in a vapor path connecting the canister and the fuel tank to each other.
A pertinent conventional vaporized fuel processing apparatus is disclosed in Japanese Laid-Open Patent Publication No. 2011-256778. The vaporized fuel processing apparatus according to Japanese Laid-Open Patent Publication No. 2011-256778 is equipped with a closing valve (control valve) provided in a vapor path connecting a canister and a fuel tank to each other. The closing valve is equipped with a dead zone region (valve-closing region) shutting off the vaporized fuel, and a conduction region (valve-opening region) allowing the vaporized fuel to pass; in the valve closing state, the fuel tank is maintained in a hermetic state; and, in the valve opening state, the vaporized fuel in the fuel tank is caused to escape to the canister side, making it possible to lower the inner pressure of the fuel tank. In the vaporized fuel processing apparatus according to Japanese Laid-Open Patent Publication No. 2011-256778, learning control is performed as follows. The degree of opening of the closing valve is changed in the opening direction at a predetermined speed from the valve-closing position; and when the inner pressure of the fuel tank begins to be reduced, the degree of opening of the closing valve is stored as the valve opening start position.
However, when the inner pressure of the fuel tank cannot be detected during the learning control, it cannot be detected when the inner pressure of the fuel tank begins to decrease. Thus, there is a case that the learning control is not completed although the closing valve is actually opened, so that an inappropriate value may be stored as the learning value. Accordingly, there has been a need for improved vaporized fuel processing apparatuses.